Joshua L. Williams

Infant Eye-tracking in the Context of Goal-Directed Actions.

This paper presents two methods that we applied to our research to record infant gaze in the context of goal-oriented actions using different eye-tracking devices: head-mounted and remote eye-tracking. For each type of eye-tracking system, we discuss their advantages and disadvantages, we describe the particular experimental setups we used to study infant looking and reaching, explain how we were able to use and synchronize these systems with other sources of data collection (video recordings and motion capture) in order to analyze gaze and movements directed toward 3D objects within a common time frame. Finally, for each method, we briefly present some results from our studies to illustrate the different levels of analyses that may be carried out using these different types of eye-tracking devices. These examples aim to highlight some of the novel questions that may be addressed using eye-tracking in the context of goal-directed actions.

Assessing the Impact of Movement Consequences on the Development of Early Reaching in Infancy

Prior research on infant reaching has shown that providing infants with repeated opportunities to reach for objects aids the emergence and progression of reaching behavior. This study investigated the effect of movement consequences on the process of learning to reach in pre-reaching infants. Thirty-five infants aged 2.9 months at the onset of the study were randomly assigned to 1 of 3 groups. Two groups received a 14-day intervention to distinct reaching tasks: (1) in a contingent group, a toy target moved and sounded upon contact only, and (2) in a continuous group, the toy moved and sounded continuously, independent of hand-toy contact. A third control group did not receive any intervention; this group’s performance was assessed only on 2 days at a 15-day interval. Results revealed that infants in the contingent group made the most progress over time compared to the two other groups. Infants in this group made significantly more overall contacts with the sounding/moving toy, and they increased their rate of visually attended target contacts relative to non-visually attended target contacts compared to the continuous and control groups. Infants in the continuous group did not differ from the control group on the number of hand-toy contacts nor did they show a change in visually attended target versus non-visually attended target contacts ratio over time. However, they did show an increase in movement speed, presumably in an attempt to attain the moving toy. These findings highlight the importance of contingent movement consequences as a critical reinforcer for the selection of action and motor learning in early development. Through repeated opportunities to explore movement consequences, infants discover and select movements that are most successful to the task-at-hand. This study further demonstrates that distinct sensory-motor experiences can have a significant impact on developmental trajectories and can influence the skills young infants will discover through their interactions with their surroundings.

Le rôle de la vision dans le développement de la préhension chez le bébé : une réévaluation

EnglishFor several decades, the role of vision in the development of infant reaching has been considered crucial. Over the past 15 years, however, this role has been questioned by a number of studies which have shown that young babies are capable of contacting objects in the dark and that, even in complete visibility conditions, they use primarily proprioceptive information to direct their arm to the target. What is therefore the role of vision in the emergence of reaching? In this article, we provide a brief review of prior work and present new data on the behavior of visual exploration and reaching in a little girl that we have followed longitudinally from the age of 10 weeks. In order to understand specifically how she used her vision during the few weeks preceding and following the emergence of reaching, we recorded her visual exploration of objects with an eye-tracker and we compared her performance to a group of 9-month-olds tested under the same conditions. Results indicate a change in object-directed visual exploration before and after the emergence of reaching. They also suggest that, over the first weeks following reaching onset, vision and action interact dynamically to create a tighter perceptual-motor mapping. francaisDepuis plusieurs decennies, le role de la vision dans le developpement de la prehension chez le bebe a ete considere comme crucial. Durant ces 15 dernieres annees, cependant, ce role a ete remis en question par des travaux qui ont montre que les jeunes bebes sont capables de contacter les objets dans le noir et que, meme dans des conditions de visibilite complete, ils utilisent principalement les informations proprioceptives pour diriger leur bras vers la cible. Quel est donc le role de la vision dans l�emergence de la prehension? Dans cet article, nous presentons des donnees nouvelles sur le comportement d�exploration visuelle et d�atteinte d�objet d�une petite fille que nous avons suivie longitudinalement des l�âge de 10 semaines. Afin de pouvoir elucider plus precisement comment elle a utilise sa vision durant les quelques semaines qui ont precede et suivi l�emergence de sa conduite de prehension, nous avons enregistre son comportement d�exploration visuelle d�objets au moyen d�un systeme d�enregistrement de mouvements oculaires (eye-tracker) et nous avons compare sa performance a celle d�un groupe de bebes de 9 mois testes dans les memes conditions. Les resultats revelent un changement du comportement visuel suite a l�emergence de la prehension. Ils suggerent egalement que des les premieres semaines de prehension, vision et action interagissent dynamiquement pour creer une correspondance spatiale perceptivo-motrice de plus en plus precise.